[webrtc-pc] Consider reverting nullable maxMessageSize (#3104)

jan-ivar has just created a new issue for https://github.com/w3c/webrtc-pc:

== Consider reverting nullable maxMessageSize ==
https://github.com/w3c/webrtc-pc/pull/3094 made `maxMessageSize` nullable and initialized to `null` instead of using the [update the data max message size](https://w3c.github.io/webrtc-pc/#dfn-update-the-data-max-message-size) algorithm.

But this was decided on faulty information in https://github.com/w3c/webrtc-pc/issues/2899#issuecomment-3993742374 about Chrome and Safari already having this behavior:
> Chrome and Safari also expose it in `"have-remote-offer"` and has nullable maxMessageSize as [decided](https://www.w3.org/2023/09/12-webrtc-minutes.html#t10):
> ```
> pc1.signalingState = "have-local-offer"
> pc1.sctp = { "state": "connecting", "maxMessageSize": null, "maxChannels": null }
> ```

A pilot error on my part: Turns out `JSON.stringify`, which I used for logging, converts `Infinity` to `null`. 🦆

My apologies. Here is the correct information https://jsfiddle.net/jib1/7oupqcm8/58:

Chrome and Safari initialize `maxMessageSize` to `Infinity`:
```
pc1.signalingState = "have-local-offer"
pc1.sctp = {state: connecting, maxMessageSize: Infinity, maxChannels: null}
pc2.signalingState = "have-remote-offer"
pc2.sctp = {state: connecting, maxMessageSize: Infinity, maxChannels: null}
pc2.signalingState = "stable"
pc2.sctp = {state: connecting, maxMessageSize: 262144, maxChannels: null}
pc1.signalingState = "stable"
pc1.sctp = {state: connecting, maxMessageSize: 262144, maxChannels: null}
```
Firefox initializes it to 65536:
```
pc1.signalingState = "have-local-offer"
pc1.sctp = {state: connecting, maxMessageSize: 65536, maxChannels: null}
pc2.signalingState = "have-remote-offer"
pc2.sctp = null
pc2.signalingState = "stable"
pc2.sctp = {state: connecting, maxMessageSize: 1073741823, maxChannels: null}
pc1.signalingState = "stable"
pc1.sctp = {state: connecting, maxMessageSize: 1073741823, maxChannels: null}
```

Both are values found in the [update the data max message size](https://w3c.github.io/webrtc-pc/#dfn-update-the-data-max-message-size), but browsers appear to be interpreting it differently.

We should probably revisit this based on corrected information.

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/3104 using your GitHub account


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Received on Thursday, 30 April 2026 22:13:15 UTC